Keep track of TextEditor focus in Alert transitions.

When transitioning from a Canvas Screen to an Alert Screen, keep track
of which TextEditor has focus. When returning to the Canvas Screen,
focus the TextEditor. This helps us match app expectations with regard
to keyboard visibility.
Merge branch 'master' of https://github.com/TimAbraldes/j2me.js into keyboard
Define converter functions for sets of pixels in the gfx scope. Fixes #676
Download JAD manifest and JAR archive at first run; store it in the FS for subsequent runs
Add tests for JAD/JAR downloading
Fix manifest parsing with entries that have ':' character in the value
Use systemXHR to circumvent CORS
Fix typo in main.js
Revert "Keep track of TextEditor focus in Alert transitions."

This reverts commit 5bee769f28e11cea283b2e1e216a7a6c6c05d6c0.
Keep track of TextEditor focus in Alert transitions.

When transitioning from a Canvas Screen to an Alert Screen, keep track
of which TextEditor has focus. When returning to the Canvas Screen,
focus the TextEditor. This helps us match app expectations with regard
to keyboard visibility.

This patch also adds plumbing to allow RunTests tests to change the
current Displayable and compare the pixels of the current screen to a
reference image. These changes allow us to convert a bunch of gfx tests
to RunTests tests. The first converted test is AlertTest, which has been
updated to also test that focus is being tracked properly across showing
Alerts.
Merge branch 'master' of https://github.com/TimAbraldes/j2me.js into keyboard
Merge branch 'master' of https://github.com/andreasgal/j2me.js into optimize_pixel_manip
Use the same parameters format for all the pixel converting functions
Remove contextToRgbData helper function
Remove rgbDataToContext helper function
Use TestHarness.setScreenAndWait from TestAlert
Fix alignment in ABGRToARGB4444 and ARGB4444ToABGR
Add newline at the end of the file
Cleanup object URLs in gfx.js

Fix for issue #694.
- Always convert images to canvases
- Cleanup object URL after conversion
Remove convertNativeImageData